The Blues defender was unhappy with the way his side conceded the opening goal at Wembley as they lost the cup to their London rivals

Alexis Sanchez benefitted from the "crazy" offside rule to score the opening goal in Arsenal's FA Cup final win over Chelsea, according to Gary Cahill, who said it should have been disallowed for a handball.

The Chilean latched on to a bouncing ball which struck his hand before he slotted past Thibaut Courtois. Aaron Ramsey was in an offside position but the referee and linesman judged him to be not interfering with play.

After Chelsea coach Antonio Conte described it as a "clear handball" adding: "I don't understand why the referee didn't decide to whistle", centre-back Cahill revealed his irritation and believes the incident changed the course of the match.

"Yes, disappointment obviously, we wanted to finish the season [well]," Cahill said. "We knew what the feeling would be like if we lost. It would put a bit of a dampener on the end of season celebrations and likewise, if we had won.

"Of course, we are disappointed. It is fresh in the mind and it is not a nice feeling. The offside rule is crazy. I spoke to a referee the other day, I forgot which game I was playing in but the ball got played through and the striker was offside.

"He made a run to it and then he's veered off to go into the box and because he has veered off then he is no longer offside. It is a bizarre rule but nevertheless, forget the offside, for me I thought it was very lucky to not be given as a handball.

"When your arms are up near your face it is an unnatural positions to be in. So yes it should have been handball."

Victor Moses was then sent off for simulation but Diego Costa a few moments later. Arsenal responded immediately, though, as Olivier Giroud came on and provided an assist a minute later for Ramsey to win the game with a diving header.

Cahill thinks Chelsea lacked the intensity required to recover from the set back of the early goal as he assessed what went wrong.

"You never know in football if they are going to come out and start nervy because it is a final," Cahill added. "Or they start with the bit between their teeth. They showed hunger in the first 15-20 minutes so credit to them for that.

"The disappointment for us was that we didn't play with the same intensity levels in the first half that we have been playing with all season. We looked slightly off the pace and it is unlike us. We are normally quick and strong and we normally build fast and everything was a little bit laboured.

"Whether that was ourselves or whether that was how well they pressed, I don't know but that was the most disappointing thing for us in the first half. Naturally it is frustrating [to concede so soon after scoring].

"We worked hard with 10 men to get back in. Energy levels, you are running off your heart there because we worked so hard to get back in. So it is devastating when that happens. It is unlike us again. When you get back in the game then that's the time to steady the ship and work again.

"It was always going to be difficult with 10 men and it wasn't to be. So we were disappointed with how quickly they went back in front.

Cahill has had a prosperous season, taking over the captain's armband from John Terry, who has had limited playing time in his final campaign.

The stand-in captain shared a trophy lift with the club icon last Sunday to win the league after a 5-1 win over Sunderland and Cahill admits that it has been a good year for him despite the recent loss.

"For sure [there are positives]," Cahill continued. "It is difficult [to say] now because we have just earned a disappointment but when I reflect then I am sure it has been a great campaign for myself and the team.

"We have won the Premier League, that's the trophy that everyone wants. We have to be proud of our 30 wins, no one has ever done that. We have to be proud of matching the 13 game win [streak]. We got the most clean sheets.

"There's loads and when you look back, there is a lot to be proud of this season. We have made huge improvements and we are back this season as the best team in the league."